1. Field of the Invention
The present invention generally relates to a mounting device including a patterned wiring film, a method of manufacturing the mounting device, and a sputtering target to be used in the manufacturing method.
2. Description of the Related Art
In recent years, semiconductor elements (such as, an LSI) have been mounted on a mounting substrate in which a plurality of single-layer substrates, each including a wiring film formed on a base of a resin, are laminated. Thus, there is a demand for a technology of forming a metal film having high adhesion to a surface of the resin. In particular, a copper thin film has an advantage of low resistance, but has low adhesion to the resin; and hence, an adhesion layer consisting of other metals is formed between the resin and the copper thin film.
FIG. 7 illustrates such a related-art mounting device 100 in which a plurality of single-layer substrates 1111 and 1112 are laminated.
Each of the single-layer substrates 1111 and 1112 of the mounting device 100 includes a base 103 consisting of the resin; and a wiring film 110 is provided on a surface of the base 103. Further, the base 103 is provided with a connection hole 102, and a metal plug 119 for connecting the wiring films 110 of the laminated single-layer substrates 1111 and 1112 to each other is provided within the connection hole 102.
FIG. 7 illustrates a state in which the base 103 of the uppermost single-layer substrate 1112 is bonded onto the single-layer substrate 1111. The base 103 is provided with the connection hole 102, and a surface of the wiring film 110 of the lower single-layer substrate 1111 is exposed from a bottom surface of the connection hole 102.
First, as illustrated in FIG. 5(b), a sputtering target containing a metal for adhesion (such, as Ti) is sputtered to form an adhesion layer 118 (such as, a Ti thin film), which is in contact with a surface of the base 103, an inner peripheral side surface of the connection hole 102, and the wiring film 110 exposed from the bottom surface illustrated in FIG. 5(a). Then, a sputtering target of copper is sputtered to form a seed layer 115 consisting of a copper thin film on a surface of the adhesion layer 118.
A patterned resist film is arranged on a surface of the seed layer 115 to expose the seed layer 115 within the connection hole 102 and the seed layer 115 at a predetermined position on the surface of the base 103, and immersed in a plating solution so that the exposed seed layer 115 is brought into contact with the plating solution; a voltage is applied between the seed layer 115 and the plating solution so that the seed layer 115 becomes negative charge with respect to the plating solution; copper is deposited on the surface of the seed layer 115 exposed by electroplating; and copper thin films 106 and 107 are formed within the connection hole 102 and on the surface of the base 103 as illustrated in FIG. 5(c). In this state, the copper thin films 106 and 107 are in contact with each other, the inside of the connection hole 102 is filled with the copper thin film 106 consisting of copper, and the copper thin films 106 and 107 are formed thicker than the seed layer 115. FIG. 3(c) illustrates a resist film 128.
In this state, the adhesion layer 118 and the seed layer 115 include portions positioned under the copper thin films 106 and 107 and portions positioned under the resist film 128, and the resist film 128 is removed to expose the seed layer 115 positioned under the resist film 128. Thereafter, first, the resultant is immersed in a copper etchant so that the exposed seed layer 115 is removed by etching while leaving a patterned seed layer 105 under the copper thin films 106 and 107, thereby resulting in the adhesion layer 118 being exposed from a portion from which the seed layer 115 has been removed, as illustrated in FIG. 5(d).
Next, the resultant is immersed in a Ti etchant for dissolving Ti so that the exposed adhesion layer 118 is removed by etching while leaving an adhesion layer 108 positioned under the copper thin films 106 and 107 and the seed layer 105, thereby resulting in the base 103 being exposed from a portion from which the adhesion layer 118 has been removed, as illustrated in FIG. 7.
The metal plug 119 filled in the connection hole 102 is composed of the adhesion layer 108, the seed layer 105, and the copper thin film 106 within the connection hole 102; and the wiring film 110 is composed of the adhesion layer 108, the seed layer 105, and the copper thin film 107 on the surface of the base 103.
The adhesion between the copper thin films 106 and 107 and the resin exposed from the surface of the base 103 is low; and the copper thin films 106 and 107 are easily separated from the resin. However, the adhesion layer 108 consisting of the Ti thin film has high adhesion to the resin and has high adhesion also to the seed layer 105 consisting of the copper thin film; therefore, the seed layer 105 and the copper thin films 106 and 107 are not separated from the base 103.
However, as is understood from the above-described manufacturing steps, in order to form the copper thin films 106 and 107, it is necessary to form two layers including the adhesion layer 108 and the seed layer 105; and hence, the wiring film 110 becomes a three-layer structure, which results in the number of the manufacturing steps increases.
Further, the adhesion layer 118 contains a large amount of elements (such, as Ti) other than copper; and therefore, the adhesion layer 118 and the seed layer 115, which is the copper thin film, cannot be etched with the same etchant, which complicates the etching process. For example, see JPA H08-332697.